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Mana Island Ecological Restoration Plan Department of Conservation P.O. Box 5086 Wellington, New Zealand

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Page 1: Mana Island Ecological Restoration Plan · Mana Island Ecological Restoration Plan ... giant pill millipede, Rhytida greenwoodi, ... Department of Conservation

Mana Island EcologicalRestoration Plan

Department of ConservationP.O. Box 5086Wellington, New Zealand

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Prepared by:Colin Miskelly

November 1998

Department of Conservation, Wellington

ISBN 0-478-01904-1

Cover photo: Tuatara. Rod Morris.

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CONTENTS page

Executive summary v

1. Introduction 1

2. Restoration options 3

3. Restoration goals 9

4. Progress with restoration 11

5. Revegetation 13

5.1 Current situation 135.2 What was Mana Island's original plant cover? 135.3 Is active replanting necessary on Mana Island? 135.4 Progress with revegetation to date 175.5 Selecting appropriate forest communities for Mana Island 195.6 A revegetation strategy for Mana Island 23

6. Restoration of non-forest communities 27

6.1 Current situation 276.2 Former distribution of non-forest plant communities 286.3 Projected extent and distribution of non-forest plant

communities 286.4 Restoring wetlands 286.5 Restoring shrubland and herbfield communities 306.6 Maintaining grasslands 30

7. Threatened plants 33

7.1 Current situation 367.2 Progress with threatened plant management

on Mana Island 367.3 Establishing populations of threatened plants

on Mana Island 37

8. Birds 41

8.1 Current situation 428.2 What was Mana Island's original avifauna? 438.3 Nationally threatened landbird species that may

require islands free of mammalian predators 438.4 A comparison with Kapiti Island 478.5 Recreating an avifaunal community for Mana island 488.6 Non-indigenous birds on Mana Island 718.7 Habitat creation for birds 718.8 Action plan 72

9. Reptiles 75

9.1 Current situation 769.2 What was Mana island's original reptile fauna? 779.3 Reptile species of the southern North Island that

may require islands free of mammalian predators 789.4 Restoring Mana Island's reptile fauna 799.5 Recreating a reptile community for Mana Island 84

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9.6 Summary of actions required to restore a diversereptile community representative of the southernNorth Island on Mana Island 94

10. Other vertebrates 97

10.1 Current situation 9710.2 Potential of Mana Island as habitat for native bats,

frogs and freshwater fish 9710.3 Recommended management action 98

11. Invertebrates 99

11.1 Current situation 10011.2 Threatened invertebrates 10111.3 Restoring invertebrate communities 105

12. Control of animal pests 107

12.1 Current situation 10812.2 Previous animal pest control programmes 10812.3 Potential animal pests on Mana Islands 109

13. Control of pest plants 113

13.1 Current situation 11313.2 Priorities for weed control 113

14. Archaeological and waahi tapu sites 115

14.1 The island's human history 11514.2 Current situation 11614.3 Conflicts between ecological restoration and

management of historic sites 11614.4 Waahi tapu 11814.5 Management actions 119

15. Fire 121

15.1 Reducing the risk of a fire occurring or spreading 12115.2 Fire suppression 121

16. Research 123

17. Community use and involvement 125

17.1 Access 12517.2 Public use and recreation 12617.3 Community involvement in ecological restoration 126

18. Summary and action plan 129

18.1 Crucial tasks 12918.2 Time frame 13018.3 Responsibilities 132

Acknowledgements 133

References 135

Appendix 1: Scientific names of animals mentioned in text 141

Appendix 2: Scientific names of plants mentioned in text 147

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Executive summary

This plan provides a philosophical basis for the planning and implementation ofecological restoration on 217 ha Mana Island. The primary goal of the restorationprogramme is to maintain those threatened species and communities that havesurvived on Mana Island within self-sustaining ecosystems similar to what arelikely to have existed on the island before human contact. Secondary restorationgoals (where compatible with the primary goal) are to:

recreate coastal forest, shoreline, cliff and wetland plant communities typical ofthe Wellington coast and similar to those expected to have occurred on thesoils and landforms present on Mana Island, using seed sources as close aspossible to (if not on) Mana Island

establish self-maintaining populations of threatened plants of the Wellingtoncoast of Cook Strait appropriate to the habitats present on Mana Island, usingseed sources as close as possible to the island (but further afield if the speciesare extinct in the Wellington region)

reintroduce or encourage colonisation by all native animal species known tohave previously occurred on Mana Island

introduce (or reintroduce) threatened and locally extinct vertebrates of thesouthern North Island that are not able to exist in the presence of introducedmammals, and are likely to have occurred in coastal habitats in the Wellingtonregion

where previously occurring vertebrate taxa are extinct, introduce anecologically similar conspecific or congeneric taxon (if one exists within NewZealand) to restore trophic processes and lost evolutionary potential

as far as possible, restore invertebrate communities typical of the plantcommunities created

introduce (or reintroduce) threatened macroinvertebrates appropriate for anisland in eastern Cook Strait.

eradicate/control animals and plants which would severely compromise otherrestoration goals

maintain grassland at priority archaeological sites to enhance interpretationand site preservation

Implementation of this suite of restoration goals should collectively restore thenatural processes necessary to recreate functional ecosystems representative of theexposed Wellington west coast before human disturbance. However, it is recognisedthat Mana Island may be required to provide habitat for a select few criticallyendangered bird species that probably or definitely never occurred on the island inthe past. Species that will or may require Mana Island to achieve short or mediumterm restoration goals include takahe, kakapo and large kiwi. Such "unnatural"introductions must not jeopardise the survival of resident and restored threatenedanimals and plants, and the species must be able to be removed totally from theisland when other more suitable (mainland or island) sites become available.

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The six key tasks required to restore viable ecosystems on Mana Island analogous towhat may have existed prior to human disturbance are: restore coastal forest; attractnesting seabirds; restore the wetland; reintroduce avian pollinators and seeddispersers; introduce a diversity of forest-dwelling invertebrates; and weed control.Introductions of other plants and animals will increase the island's potential formaintaining indigenous biodiversity, but these six actions are fundamental torestoring ecosystem viability because of the species and processes that aredependent on their successful implementation.

Forest cover will be artificially restored to about a third of the island using a mix ofabout 45 tree and shrub species considered appropriate for the landforms and soilson Maria Island. All source populations will be on the island (preferably) or from theadjacent mainland coast. Predominant canopy species will be kohekohe, tawa andkaraka.About 400,000 further plants are required to complete revegetation of 72 ha,and planting of canopy and subcanopy species should be complete by 2007A.D.

Restricting planting of woody species to 72 ha will create a mosaic of habitats thatwill provide a variety of habitats suitable for the range of plant and animal speciesthat are either resident on the island or considered appropriate for introduction. It isanticipated that the combined effects of the planting programme and naturalregeneration will produce about 76 ha of coastal broadleaved forest and 84 ha ofshrublands within the next 30-40 years, leaving about 57 ha of grassland. Naturalsuccession will continue to reduce the area of open grassland over time. The onlysites where regeneration of native shrub and tree species will be actively preventedis on archaeological sites unless Mana Island remains a key site for the conservationof takahe.

The main wetland (Waikoko) on Mana Island will be restored to provide habitat freeof mammalian predators and browsers for brown teal, North Island fernbird, brownmudfish and a variety of threatened wetland plants of the Cook Strait and WellingtonEcological Districts. About 80 regionally threatened vascular plant species (bothterrestrial and wetland) are recommended for introduction. Priority species includeAcaena juvenca, A. pallida, Jersey fern, Atriplex buchananii, A. cinerea, Clematisafoliata, Convolvulus verecundus, Coprosma acerosa, matagouri, akeake,Euphorbia glauca, fleostylus micranthus, Leptinella nana, L. pusilla, rohutu,Muehlenbeckia astonii, M. ephedroides, Pimelea aridula, Rhabdotbamnussolandri, Rytidosperma petrosum, kowhai (Kapiti Island form), Tetragoniatetragonioides and Tupeia antarctica.

Thirty-three animal species are recommended for introduction or attraction to ManaIsland: 18 birds, seven reptiles, one fish and seven macroinvertebrates. Of these, ninewill be sourced from the eastern Cook Strait Ecological District (mainly KapitiIsland; little spotted kiwi, New Zealand pigeon, kaka, whitehead, robin, bellbird, tui,Whitaker's skink, speargrass weevil) and 16 will be sourced from elsewhere in theSounds-Wellington Ecological Region (fluttering shearwater, fairy prion, divingpetrel, gannet, banded rail, yellow-crowned parakeet, Cook Strait tuatara, speckledskink, spotted skink, Duvaucel's gecko, Wellington green gecko, flax weevil, Lissotesreticulatus, giant pill millipede, Rhytida greenwoodi, Wainuia urnula). Six speciesare no longer present in the ecological region and will be sourced from furtherafield (brown teal, shore plover, North Island fernbird, robust skink, brown mudfish,Powelliphanta traversi). The two remaining recommended introductions (ChathamIsland snipe and rock wren) will replace extinct taxa.

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Restoration of diverse invertebrate communities will require mass translocationtechniques rather than a species-by-species approach. It is recommended that littersamples, decaying timber and malaise trap samples be collected in appropriate foresttypes on Kapiti Island and transferred to Mana Island. Thorough screening duringtransfer will check for the presence of injurious adventive species, and allowdocumentation of the species transferred.

Control of animal and plant pests is a crucial component of ecological restorationon Mana Island. Current management issues for animal pests include limiting theimpacts of the large black-backed gull and pukeko populations, and contingencymeasures to prevent colonisation by rodents and vespulid wasps. Weed controlcurrently focusses on boxthorn and karo, but equal or higher priority should begiven to eradicating those weed species that have not yet become widely distributedon the island (especially brush wattle, bone-seed, broom, blackberry, holly-leavedsenecio, wandering Jew and gorse).

The ecological restoration plan has made allowance for protection of knownhistoric sites, and is considered compatible with a high level of public visitation andparticipation. Indeed, the close involvement of the local community and iwi is andwill be essential for the ecological restoration of Mana Island to succeed.

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1. Introduction

Mana Island is a 217 ha Scientific Reserve administered by Wellington Conservancy,Department of Conservation. Mana Island lies about 4 km offshore from Titahi Bay,and is 2.5 km from Green Point, the nearest part of the North Island coast. Theisland has resident Department of Conservation staff. Ngati Toa are the tangatawhenua.

Mana Island has a long history of Maori and European occupation (Jones 1987) andwas farmed from 1832 until the last stock were removed in 1986. This 154 years ofintensive pastoralism created a highly modified and degraded ecosystem, withindigenous vegetation confined almost entirely to the cliffs and one small catchment(Timmins et al. 1987a). The human history of the island has been well summarisedby Day (1987).

Given the long period that Mana was farmed, it is surprising that mice* were theonly mammals present when farming ceased. Mice were eradicated from Mana bypoisoning in 1989/90 (Todd & Miskelly in press); the island is considered to havebeen totally free of introduced mammals since February 1990. The island is asignificant habitat for three resident threatened animal species (Cook Strait giantweta, McGregor's skink and goldstripe gecko) and is a breeding site for sevenspecies of sea and coastal birds. Mana Island is also an important site for severalnationally and regionally threatened plant taxa including Cook's scurvy grass, large-leaved milk tree, rengarenga and Melicytus obovatus.

The relative accessibility of Mana Island has allowed considerable publicinvolvement in restoration there, particularly the ongoing revegetation programme.Restoration on Mana Island to date has been guided by a variety of managementdocuments, including: Department of Lands & Survey 1981 & 1986; Timmins et al.1987b; and Nicholls 1989. All these were written prior to mouse eradication, andnone established an overall restoration goal. This report is based on a workshopheld at Wellington Conservancy in July 1992, and is intended as a basis forrestoration action on Mana Island for the next thirty years, after which minimalecological management should be required. It is expected that this restoration planwill continue to evolve as we learn from each stage, and so the conclusions andactions outlined here should not be considered the final word.

This restoration plan provides an overall strategic framework for ecologicalrestoration on Mana island, but further levels of operational planning will berequired before new conservation actions occur on the island. For example, speciesintroductions will each require completion and approval of a species transferproposal, the planting programme requires planning and co-ordination of seedcollection, propagation and community structure appropriate for each planting site,and restoration of the wetland will require detailed surveying, production of adevelopment plan and granting of resource consents. However, as all futurerestorative actions on the island will be carried out within the philosophicalframework outlined here, establishing priorities for resourcing and obtainingapprovals for the next tier of operational plans should be considerably streamlined.

' Scientific names of animals and plants are given in appendices

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2. Restoration optionsEcological restoration can be defined as active intervention to restore lost species orlost physical conditions in order to recreate a biotic community that previouslyexisted (Atkinson 1988). This definition separates ecological restoration fromecological protection which may involve removing or excluding unwanted speciesor threats, and from natural restoration which involves processes such asregeneration and succession (Atkinson 1995). Ecological protection and naturalrestoration are extremely important components of the ecological management ofan area, and are often the only cost-effective means to restore conservation valuesover large land areas. However, where ecological systems have been badly damaged,and component species and processes have been lost, ecological restoration may benecessary (alongside ecological protection and natural restoration) if a previouslyexisting biotic community is to be recreated. Ecological restoration implies thatonly those plant and animal species that would have occurred previously at the siteare introduced; this contrasts with revegetation or rehabilitation planting, where amix of local plus indigenous plants from other Ecological Districts and alien plantspecies could be used. On New Zealand islands where introduced mammals havebeen eradicated the usual goal of ecological restoration is to recreate a bioticcommunity that may have existed before human contact occurred (Atkinson 1990).

This rather restrictive definition of ecological restoration can rarely be achieved inthe real world because: (a) we do not usually know the exact composition andstructure of the community we are aiming to recreate, (b) some of the speciesoriginally present are likely to be extinct, (c) there are likely to be introduced birds,invertebrates and plant species present that either cannot be eradicated or willcontinue to colonise, (d) environmental conditions have changed through the globaleffects of industrialisation, and (e) there may be demands for mammal-free islandsfor critically endangered species that did not occur naturally at that site. These andother constraints on ecological restoration were discussed by Simberloff (1990) andAtkinson (1990). Simberloff suggested that ecological restoration could beconsidered a success if the structure and function of the system produced cannot beshown to be outside the bounds generated by the normal dynamic processes ofcommunities and ecosystems. With respect to Mana Island, this would mean that theecosystem produced by ecological restoration should be indistinguishable from onethat may have occurred if the island had never been cleared and mice and stocknever introduced. This approach allows considerable latitude during restoration, asproof of previous existence is not required (as long as there is sufficient evidencethat the species in question is likely to have been present), and local extinctions andimmigration are likely to alter community composition naturally over time.However, it is still essential to identify the goal of the restoration programme(Atkinson 1988 & 1990).

Extinction of a previously existing taxon may not preclude restoration, asreplacement with an extant closely related species or subspecies (see Atkinson 1988& 1990) may fill the triple roles of establishing a further population of a threatenedspecies, restoring some of the trophic processes formerly present, and restoring lostevolutionary potential. This surrogate species concept was developed by Atkinsonto support the introduction of rock wren to Matiu/Somes and/or Mana Islands toattempt the re-establishment of a lowland, forest-dwelling wren to replace theextinct bush wren. A similar case could be argued for the introduction of ChathamIsland snipe to Mana Island to replace the extinct North Island form of New Zealandsnipe.

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Introductions of surrogate species to restore lost evolutionary potential have not yetbeen attempted in New Zealand, but there have been many examples ofintroductions of threatened species to islands (including Mana Island) where there islittle likelihood that the species ever occurred previously. The introductions of, e.g.,takahe and kakapo to islands are in direct conflict with ecological restorationprogrammes as, even if there is evidence for their previous existence within therelevant Ecological District, it is doubtful whether small islands could support viablepopulations of species with such large space requirements. There are many NewZealand animal and plant species that are critically endangered by the presence ofintroduced mammal species and for which introduction to predator-free islands maybe the only option for retaining a viable wild population. However, the increasingefficiency with which islands are being cleared of rodents and other pests (Table2.1) means that predator-free habitats are being created within appropriateEcological Districts for many threatened taxa, reducing the need for inappropriateintroductions.

TABLE 2.1 NEW ZEALAND ISLANDS OVER 100 ha IN SIZE THAT ARE CURRENTLYTHOUGHT TO BE FREE OF INTRODUCED MAMMALS (OUTLYING ISLAND GROUPSNOT INCLUDED).

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ISLAND AREA (ha) HISTORY OF MAMMAL ERADICATIONS AND LAND USE

Great (Three Kings) 408 Goats eradicated 1946. Regenerating forest.

Tawhiti Rahi 163 Introduced mammals never present. Forested.

Aorangi 110 Pigs eradicated 1936. Forested.

Whatupuke 102 Kiore eradicated 1993 Forested .

Tiritiri Matangi 196 Kiore eradicated 1993. Part forested. Formerly farmed.

Cuvier 170 Goats eradicated 1961, cats 1964, kiore 1993. Forested. Part formerly farmed.

Red Mercury 225 Kiore eradicated 1992. Forested.

Stanley 100 Kiore & rabbits eradicated 1991. Forested.

Moutohora 173 Goats eradicated 1977, Norway rats 1986, rabbits 1987. Formerly farmed.

Kapiti 1966 Axis deer eradicated 1906, cattle 1917, goats 1928, cats 1934, sheep 1969, possums1986. Kiore and Norway rat eradication attempted 1996. Forested.

Mana 217 Mice eradicated 1990. Formerly farmed.

Stephens 150 Cats eradicated 1925. Formerly farmed.

Nukuwaiata 242 Pigs eradicated 1963, More (and weka) eradicated 1993. Forested.

Maud 309 Stoats eradicated 1983 & 1993. Part forested. Formerly farmed.

Breaksea 170 Norway rats eradicated 1988. Forested.

Solander 100 Introduced mammals never present. Weka present. Part forested.

Ulva 259 Norway rats eradicated 1995. Forested.

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There are a few critically endangered species (e.g., kakapo, takahe and some kiwitaxa) for which their may be no ecologically or biogeographically appropriateislands available, and where there will inevitably be conflicts between speciesrecovery programmes and island restoration programmes. For these taxa it isessential that there is national co-ordination of suitable islands where there aresufficiently few conflicts between existing conservation values and the speciesproposed for introduction. In such an analysis it is inevitable that islands with aprevious history of extreme modification (e.g., Tiritiri Matangi, Cuvier, Moutohora,Mana and Maud Islands) are likely to be selected for "extralimital" introductions overislands that have retained largely unmodified ecosystems.

Atkinson &Towns (1990) described a scheme for classifying islands of conservationsignificance into functional categories on the basis of the presence or absence ofendemic species, introduced mammals and indigenous habitats, vulnerability tohuman interference, degree of habitat modification, and opportunities for habitatrestoration (Table 2.2). These categories are points on a continuum, but Atkinson &Towns specifically mentioned Mana as an example of a restoration island. The keydifference between restoration islands and open sanctuary islands is whether theecosystem created is an approximation of an ecosystem that formerly existed, orwhether the primary purpose is to create habitat for threatened species that maynot have formerly existed at that site. As Mana Island has retained nationallysignificant populations of threatened animals, and regionally significant populationsof threatened plants, it is more appropriate to use these as a basis for restoring aformer Mana Island ecosystem, rather than creating an artificial biotic assemblage.

TABLE 2.2 CRITERIA FOR CLASSIFYING ISLANDS OF CONSERVATION SIGNIFICANCEI NTO FUNCTIONAL CATEGORIES (AFTER ATKINSON 1990).

Atkinson &Towns' (1990) management suggestions for restoration islands are givenin Table 2.3. Note that they specifically mention the introduction of selected speciesof nationally endangered animals as appropriate for restoration islands, even thoughthis may conflict with the overall goal of restoring a biotic community that may havepreviously existed at that site. The potential for conflict between species recovery

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FUNCTIONAL CATEGORY CRITERIA FOR RECOGNITION

Minimum impact islands Presence of island endemics; freedom from introduced mammals; significant areas ofindigenous habitat; high vulnerability to human interference; all sizes of islands, both modifiedand largely unmodified

Refuge islands Presence of mainland endemics as island survivors; introduced mammals sometimes present;significant areas of indigenous habitat; moderate vulnerability to human interference; all sizesof islands; all degrees of modification except those largely unmodified

Restoration islands Opportunities for restoring habitats of threatened species and for restoring threatenedcommunities, both those of islands and those of the mainland; modified and extremelymodified islands of all sizes

Open sanctuary islands Opportunities for providing habitats for rare and threatened species; opportunities for publiceducation; medium and large islands, both modified and extremely modified

Multiple use islands Conservation values secondary to other uses such as farming, forestry and recreation. Mostlyextremely modified islands that are sometimes farm parks or privately owned

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programmes and strict island restoration on Mana Island has been discussedextensively by Timmins et al. (1987b), Atkinson (1988 & 1990) and Towns et al.(1990).

The most widely accepted conceptual framework for guiding ecological restorationin New Zealand is the Ecological Region/Ecological District system (McEwen 1987).On the basis of soil, vegetation, climate, landform and cultural modification, NewZealand is divided into 268 Ecological Districts which are grouped into 85Ecological Regions. Many island restoration programmes identify species orcommunities from the relevant Ecological District or Ecological Region asappropriate for restoration, even if there is no definite evidence of their formerpresence on the island (e.g., Timmins et al. 1987b; Atkinson 1988; Smale & Owen1990; McGlynn 1990). Under the current system, Mana Island is part of the CookStrait Ecological District within the Sounds-Wellington Ecological Region. CookStrait Ecological District incorporates Kapiti and Maria Islands, the exposed coastand adjacent slopes between Paekakariki and Owhiro Bay, plus Stephens, Rangitoto,Trio, Chetwode, Titi and Brothers Islands, and headlands of the outer MarlboroughSounds. Sounds-Wellington Ecological Region is comprised of four EcologicalDistricts that include the Hutt Valley, Matiu/Somes Island, the Wellington peninsula,and the entire Marlborough Sounds.

TABLE 2.3 MANAGEMENT ACTIONS APPROPRIATE FOR A RESTORATION ISLAND(FROM ATKINSON &TOWNS 1990).Note that .for Mana Island "introduced" refers to species from beyond the eastern Cook StraitEcological District and local species that are unlikely to have naturally occurred on a smallisland.

*i.e., species unlikely to have been present on the island originally

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Primary conservation function Recovery of viable populations of threatened species and restoration of particular communities

Protective action for species Precautions against establishment of introduced plants and animals (with certainand biotic communities exceptions, see below) and against illegal visits and fires

Protective and restorative action Sites of archaeological value protected with restoration of selected sites where there will befor archaeological sites minimal diruption to existing or restored biotic communities

Restorative action for Restoration of communities formerly present and extension of some still existingbiotic communities

Translocation of plants Not permitted except for providing temporary cover or, in exceptional circumstances, tonot natural to the island` provide food for a nationally endangered animal species

Translocation of animals Permitted for selected species of nationally endangered animalsnot natural to the island'

Habitat manipulation for Choice of communities to be restored sometimes influenced by habitat requirements ofparticular species threatened species

Scientific activity Experimentation using carefully monitored trials to measure progress of programme

Education and interpretation (i) Low impact activities not possible in an open sanctuary(ii) Permitted visitors to a few selected islands with interpretation/supervision by rangers(iii) Volunteer help with restoration work on some islands

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Cook Strait Ecological District was defined on the basis of its climate (exposure tosevere gales) topography and vegetation: "the boundaries recognise ecological andfloristic affinities between the very exposed, steep coastal escarpments, terraces,headlands and islands on either side of Cook Strait" (McEwen 1987). However, thereis a very marked faunal discontinuity across Cook Strait (discussed below under"Birds" and "Reptiles") and there is considerable disagreement over whether the twosides of Cook Strait should be included in the same Ecological District (Ogle 1989a;Atkinson 1992). Botanists have long argued that seed sources as close as possible tothe restoration site should be used (Godley 1972; Timmins & Wassilieff 1984;Timmins et al. 1987b), therefore there are compelling floral and faunistic reasonsfor not using the entire Cook Strait Ecological District (or Sounds-WellingtonEcological Region) as a model for restoring Mana Island. Some species that arelocally extinct on Maria Island and the southern North Island may have to besourced from the Marlborough Sounds (e.g., tuatara, Duvaucel's gecko and severalspecies of burrowing petrels), but this is a separate issue from using, e.g., theBrothers islands or Stephens Island as models for restoring biotic communities onMaria Island.

Ian Atkinson (in lit. July 1992) suggested that for the purposes of ecologicalrestoration on Mana Island, Mana and Kapiti Islands and the coast betweenPaekakariki and Sinclair Head should be included in an expanded WellingtonEcological District (i.e. including Wellington peninsula, the Hutt Valley, and islands inPort Nicholson). This would still leave the boundaries of the Sounds-WellingtonEcological Region to draw attention to the important ecological similarities betweenthe North and South Islands in the Cook Strait region.

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3.

Restoration goals

The primary restoration goal for Mana Island is to maintain those threatenedspecies and communities that have survived on Mana Island within self-sustaining ecosystems similar to those likely to have existed on the island beforehuman contact.

Secondary restoration goals (where these are compatible with the primary goal) are:

recreate coastal forest, shoreline, cliff and wetland plant communities typical ofthe Wellington coast and similar to those expected to have occurred on thesoils and landforms present on Mana Island, using seed sources as close aspossible to (if not on) Mana Island

establish self-maintaining populations of threatened plants of the Wellingtoncoast of Cook Strait appropriate to the habitats present on Mana Island, usingseed sources as close as possible to the island (but further afield if the speciesare extinct in the Wellington region)

reintroduce or encourage colonisation by all native animal species known tohave previously occurred on Mana Island

introduce (or reintroduce) threatened and locally extinct vertebrates of thesouthern North Island that are not able to exist in the presence of introducedmammals, and are likely to have occurred in coastal habitats in the Wellingtonregion

where previously occurring vertebrate taxa are extinct, introduce anecologically similar conspecific or congeneric taxon (if one exists within NewZealand) to restore trophic processes and lost evolutionary potential

as far as possible, restore invertebrate communities typical of the plantcommunities created

introduce (or reintroduce) threatened macroinvertebrates appropriate for anisland in eastern Cook Strait

eradicate/control animals and plants which would severely compromise otherrestoration goals

maintain grassland at priority archaeological sites to enhance interpretationand site preservation

This suite of restoration goals should collectively restore the natural processesnecessary to recreate a functional ecosystem representative of the exposedWellington west coast before human disturbance. However, it is recognised thatMana Island may be required to provide habitat for a select few critically endangeredbird species that probably or definitely never occurred on the island in the past. Iftaxa that are not likely to have ever occurred on Mana must be introduced to ensuretheir survival, they must (a) not jeopardise the survival of resident and restoredthreatened animals and plants, and (b) be able to be removed totally from Manawhen other more suitable (mainland or island) sites are available.

The close involvement of the local community and iwi is and will be essential forthe ecological restoration of Mana Island to succeed.

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4. Progress with restoration

Over 250,000 plants of at least 50 species have been planted on Maria since 1987 aspart of the revegetation programme. Plantings have mainly been confined to valleysides and floors. Survival in the first year of planting averaged about 80% beforepukeko became numerous (P Todd pers. comm.), but has since declined due toextensive damage by pukekos.

The eradication of mice has resulted in dramatic increases in populations of all threethreatened animal species known to be present: Cook Strait giant weta, McGregor'sskink and goldstripe gecko (Whitaker 1993; Newman 1994; Todd & Miskelly inpress). Anecdotal evidence indicates that several species of native invertebrates inaddition to the giant weta have increased since mouse eradication; this wasinvestigated further during surveys in November 1993 & February 1994.

Three species of endangered native landbirds have been introduced to Mana (takahe,kakapo and little spotted kiwi), but none has yet established a self-sustainingpopulation. There are currently no kakapo on Mana. North Island robins werereintroduced to Mana Island in 1995 and 1996, when 68 were transferred fromKapiti Island.

Breeding success and population size of sooty shearwaters at the southern colony(c.100 pairs) are being monitored annually. The northern colony (< 10 pairs) wasrecently rediscovered 18 years after it was last recorded as being active. An attempthas been made to attract other species of burrowing petrel to the island at one siteusing continuous broadcast of recorded calls at night, and an attempt to attractgannets to an artificial colony commenced in 1997.

The suitability of Mana Island for the release of captive-reared and captive-bredshore plover was the subject of a study in 1993/94 (Miskelly & Aikman 1993). Themain factor that was considered likely to jeopardise establishment of shore ploverwas the high density of breeding black-backed gulls. Gull control was initiated onMaria Island in 1994/95 in preparation for shore plover release.

Weed control on Mana Island has been a major focus since 1994, with a dedicatedteam working on boxthorn removal each summer since then. Colonising weedspecies are also targeted to prevent new weed species becoming established.

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5. Revegetation

5.1

CURRENT SITUATION

The vegetation of Mana Island was described by Timmins et al. (1987a) based onsurveys between 1984 and 1986. The shoreline and cliffs are mainly covered inregenerating Mueblenbeckia complexa - Coprosma propinqua shrubland. Taupata,tauhinu, Tetragonia trigyna and Melicytus crassifolius are also common, andboxthorn is a major component of shrub communities on the north and north-eastcoasts. The valleys are mainly covered in exotic grasslands dominated by cocksfoot,Yorkshire fog, prairie grass, rye grass and white clover. Weta Valley, Tauhinu Valleyand the top of Forest Valley have some shrub cover of tauhinu, manuka and kanuka.In Forest Valley this grades into 6-7 m tall kanuka with an understorey of nativeshrubs, then a small (< 1 ha) area of kanuka forest up to 12 m tall containing anarrow band of broad-leaved trees (karaka, two large-leaved milk trees and one eachof kohekohe and wharangi). The plateau is almost totally covered in rank exoticgrasses and clover. Shelterbelts of pine and macrocarpa were planted earlier thiscentury, and more recent shelter belts of toetoe, pampas grass, flax and Tasmanianngaio were planted when the island was being run as a quarantine research stationby the Ministry of Agriculture and Fisheries in the 1970s.

Timmins et al. (1987a) recorded 325 vascular plant species from Mana Island, ofwhich 171 (53%) were native. Only 40 species of native trees and shrubs wererecorded (Table 5.1) and, of these, 17 species were recorded at fewer than five sites.The native flora of Maria Island is thus very restricted and unlikely to include the fulldiversity once present.

5.2

WHAT WAS MANA ISLAND'S ORIGINAL PLANT COVER?

The original vegetation of Mana Island is not known. Palynological studies revealeda predominantly manuka/kanuka community from 560 ± 160 years BP untilEuropean settlement (Chester & Raine 1990; Chester 1991). This manuka/kanukacommunity (similar to that found in the one forested catchment on the island) wasprobably a seral community established after the original forest was burnt, althoughearlier pollen sequences have not been located. Mixed broadleaved/podocarp forestis more typical of small islands (Chester 1991), and some of the likely canopyspecies (akiraho, karaka, kohekohe, large-leaved milk tree, wharangi and kaikomako)are present on Mana in small numbers (Timmins et al. 1987a).

5.3

IS ACTIVE REPLANTING NECESSARY ON MANA ISLAND?

Active revegetation is necessary on Mana because the landscape is so extensivelymodified, and because there is a low diversity of native woody plant species on theisland. Natural regeneration of the forest and scrub vegetation on Mana would takemany decades, if not centuries, and is unlikely to produce a diverse broadleaved/

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podocarp forest such as was likely to have been present originally. Revegetation willalso provide habitat for forest- and scrub-dwelling species more rapidly than naturalregeneration.

TABLE 5.1 NATIVE TREE AND SHRUB SPECIES PRESENT ON MANA ISLAND IN1984-86, WITH NOTES ON DISTRIBUTION AND ABUNDANCE (FROM TIMMINS ET AL .1987a).

1 4

SPECIES COMMENT

Titoki One seedling recorded 1975

Rangiora Abundant in Forest Valley

New Zealand broom Many in Forest Valley

Tauhinu Abundant on shore, cliffs and valleys

Coprosma areolata One in Forest Valley

C. lucida Many in Forest Valley; present on cliffs

C propinqua Abundant on shore, cliffs and valleys

C. rhamnoides Abundant in Forest Valley; present on cliffs

Taupata Abundant on shore and cliffs and as plantings

Karamu Many in Forest Valley; elsewhere as plantings

Tree tutu One plant recorded 1911

Cabbage tree One on south-east cliff face; elsewhere as plantings

Karaka Many in Forest Valley; present on cliffs; elsewhere as plantings

Prickly mingimingi Many on cliffs and on rocky outcrops in valleys

Kohekohe One tree and many seedlings in Forest Valley

Puka One at mouth of Tauhinu Valley and one on northern cliffs

Koromiko Many on cliffs

Lacebark Present on shore; elsewhere as plantings

Kanuka Many on cliffs and in valleys; abundant in Forest Valley

Manuka Abundant on cliffs and in valleys

Patotara Many on cliffs and in valleys

Kawakawa Abundant in Forest Valley; present on cliffs

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TABLE 5.1 CONTINUED

However, there are many plant and animal species on Mana Island that do not thrivein forest habitats„ e.g., Melicytus obovatus, speargrass, giant weta and takahe, andrestoring forest to the entire island would also limit restoration opportunities forspecies such as Mueblenbeckia astonii, shore spurge, fernbird, brown teal andsnipe. For these reasons, active planting of tree and shrub species is planned foronly about 72 ha (33%) of Mana Island (Figure 5.1). Areas to be specifically excludedfrom the main revegetation programme are: (a) the shore line and cliffs (61 ha)which have extensive native shrub, herb and grass communities, (b) the south sideof Weta Valley and the lower reaches of Forest and Tauhinu Valleys (19 ha) wherenatural succession is restoring shrub and forest communities, (c) archaeological sites(c.5 ha) where woody vegetation could obscure surface features and disturbsubsurface strata, (d) the middle reaches of Astons Valley and Tauhinu Valley (25 ha)as control areas to assess natural regeneration of grassland in sheltered sites, (e)rocky outcrops and steep slopes with thin soils (c. 1 ha) within the main planting

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Wharangi One tree in Forest Valley; seedlings in Forest Valley and nearby cliffs

Melicytus crassifolius Abundant on shore and cliffs; present in valleys

M. obovatus Eight on cliffs, one on shore

Mahoe Many in Forest Valley; present on cliffs and shore

Northern rata One on south-east cliff

Ngaio Recorded in 1975 on south-east cliffs; elsewhere as plantings

Mapou Two trees in Forest Valley; 16 saplings on shore, cliffs and valleys

Akiraho Many on cliffs and in Forest Valley

Coastal tree daisy Two on south-east cliffs; patch inAston Valley, plus two others in valleys

Large-leaved milk tree Two trees and many seedlings in Forest Valley; one tree on cliffs and one in valley

Kaikomako Nine on shore, four on cliffs, many in northern valleys

Pinatoro Many on cliffs and in valleys

Karo Widely planted

Shore ribbonwood One on south-east shore in 1986

Five finger Recorded in 1911; more recently as plantings

Solanum aviculare Many on shore and valleys; few on cliffs

S. laciniatum Many on shore and valleys; few on cliffs

Ongaonga Many in valleys; few on shore

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Figure 5.1 Areas of Mana Island planned for planting of tree and shrub species as part of the restorationprogramme.

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area, where native shrubs and herbs are already establishing, (f) most (35 ha) of theplateau grasslands where strong salt-laden winds and dry summer conditions willrestrict establishment of shrub and forest cover, and (g) windows of grassland onvalley floors and lower slopes to provide feeding areas for takahe.

Restricting planting of woody species to 72 ha will create a mosaic of habitats that isboth appropriate for the local landforms, soils and microclimates on the island, andwill provide a variety of habitats suitable for the range of plant and animal speciesthat are either resident on the island or considered appropriate for introduction. Itis anticipated that the combined effects of the planting programme and naturalregeneration will produce about 76 ha of coastal broadleaved forest and 84 ha ofshrublands within the next 30-40 years (Figure 5.2), leaving about 57 ha of grassland.Natural succession will continue to reduce the area of open grassland over time, butthe only sites where regeneration of native shrub and tree species will be activelyprevented is on archaeological sites, unless Mana Island remains a key site for takaheconservation beyond the medium term.

5.4

PROGRESS WITH REVEGETATION TO DATE

The emphasis of the revegetation programme is on recreating plant communitiesappropriate to the island's location, climate, soils and landforms. Seed is collectedon the island or on the adjacent coast (all within Cook Strait Ecological District). Allseed is collected from sites below 200 m asl, and from areas with similar soils tothose of Mana Island. Mainland seed sources are used only if the species does notoccur on Mana Island. Most seed is germinated off the island and the seedlingsreturned to the island, where they are pricked out and raised for a further 1-2 yearsbefore being planted out. Herbicides are no longer used to remove grasses beforeplanting. Initial plantings are of seral species (Table 5.2) to overtop the rank grass,attract birds and provide suitable microhabitats for eventual canopy species tobecome established. Some interplanting of canopy species (e.g., wharangi, kahikateaand tawa) under earlier plantings has also occurred to provide a seed source so thatnatural processes (e.g., seed dispersal by fruit-eating birds) will dictate the eventualforest composition (see Wright & Cameron 1990). Effort has been put into creatinga corridor between Forest Valley and the longest established plantings near thehouses. Over 200,000 plants of 50 species were planted in about 30 ha between1987 and 1996 (Table 5.2).

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Figure 5.2 Projected forest and scrub cover on Mana Island in 2030 A.D. if ecological restoration is completed asplanned.

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TABLE 5.2 SUMMARY OF REVEGETATION EFFORT ON MANA ISLAND, 1987 TO 1996.

5.5

SELECTING APPROPRIATE FOREST COMMUNITIES FORMANA ISLAND

Plant communities within a region are often determined by physical parameterssuch as soil type, slope, aspect, drainage and exposure to wind (references in Meurk& Blaschke 1990), and restoration programmes should be stratified according to thelandforms, soils, microclimate and drainage patterns within the island. Experiencefrom the first ten years of the planting programme provides a more realistic basis forplanning a reviewable revegetation strategy based on site factors and anticipatedlandscape character.

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YEAR NUMBER SPECIESOF PLANTS

1987 11,500 Titoki, rengarenga, rangiora, tauhinu, Coprosma lucida, taupata, karamu, cabbage tree, pigeonwood,kanuka, manuka, ngaio, kohuhu, five finger

1988 27,000 Rangiora, taupata, karamu, kanuka, manuka, kawakawa, wharangi, mahoe, ngaio, akiraho, kaikomako,wharariki, harakeke, five finger

1989 15,000

1990 20,000 Titoki, Coprosma lucida, taupata, karamu, karaka, kahikatea, kanuka, manuka, wharangi, mahoe, ngaio,mapou, five finger, kowhai

1991 22,000 Coprosma propinqua, kohekohe, wharangi, ngaio, five finger, lancewood

1992 23,900 Tawa, tree Lucerne, C. propinqua, taupata, karamu, cabbage tree, toetoe, karaka, kahikatea, kohekohe,puka, kanuka, kawakawa, wharangi, mahoe, ngaio, mapou, kaikomako, kohuhu, five finger, kowhai

1993 17,000 Tawa, rangiora, putaputaweta, Coprosma lucida, C. propinqua, taupata, karamu, cabbage tree, karaka,kahikatea, koromiko, pigeonwood, kanuka, kawakawa, wharangi, mahoe, ngaio, mapou, wharariki,kohulm, totam, five finger, kowhai

1994 13,500 Tawa, Coprosma lucida, C. propinqua, taupata, karamu, karaka, kahikatea, kohekohe, puka, koromiko,kanuka, Cook's scurvy grass, manuka, wharangi, Melicytus crassifolius, mahoe, ngaio, akiraho,kaikomako, lemonwood, kohuhu, totara, five finger, lancewood

1995 27,800 Rengarenga, tawa, Carex sp ., Carmichaelia arborea, Coprosma lucida, C. propinqua, taupata,karamu, cabbage tree, toetoe, karaka, kahikatea, kohekohe, puka, koromiko, pigeonwood, kanuka,Cook's scurvy grass, manuka, mahoe, ngaio, akiraho, Olearia solandri, wharariki, lemonwood, kohuhu,totara, five finger, lancewood, nikau, kowhai

1996 29,800 Rengarenga, tawa, Carex sp ., Carmichaelia arborea, tauhinu, Clematis forsteri, Coprosma lucida,C. propinqua, C. rhamnoides, taupata, karamu, cabbage tree, toetoe, karaka, kahikatea, turutu,kohekohe, hangehange, puka, koromiko, pigeonwood, kanuka, Cook's scurvy grass, manuka,kawakawa, wharangi, harakeke, Melicytus obovatus, mahoe, ngaio, akiraho, Olearia solandri,wharariki, kohuhu, miro, five finger, poroporo, large-leaved milk tree

Total 207,500

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There are four soil types present on Mana Island (Figure 5.3; based on Heine 1975):Paremata silt loam, Porirua fine sandy loam, Terawhiti steep-land soils and Titahi hillsoils. To aid restoration of forest communities on Mana Island, Gabites (1994)surveyed vegetation communities at 12 sites on the adjacent mainland in relation tosoil type, gradient, aspect, drainage and exposure. Gabites' results have beencombined with Ogle's (1985) surveys of forest remnants in the Plimmerton area toproduce the species lists in Table 5.3. On all four soil types kohekohe was adominant canopy species along with tawa, karaka or ngaio. Other canopy speciesincluded wharangi, kaikomako, titoki, miro and kohuhu. The most abundantsubcanopy species were kawakawa, hangehange, mahoe, rangiora, pigeonwood andCoprosma species. Important seral species during forest establishment includedmahoe, manuka, kanuka, koromiko, five finger and small-leaved Coprosma species.Lianes present at all sites included Metrosideros fulgens, aka, kaiwhiria andsupplejack. Of the 69 native woody species recorded by Ogle (1985) and Gabites(1994) 36 occur naturally on Mana Island (Timmins et al. 1987a); the remaining 33species, which may be candidates for the revegetation programme on Mana Island,are listed in Table 5.4. Two tree species already used in the revegetation programme(lemonwood and kowhai) were not recorded by Gabites (1994) from the 12 sitesshe surveyed and do not occur naturally on Mana Island, but are present elsewherein the Cook Strait Ecological District (e.g., on Kapiti Island); these two speciesshould be used sparingly in the Mana Island revegetation programme.

Within each soil type Gabites (1994) found that other physical factors influencedcommunity structure. Kohekohe was prevalent on sites that were very exposed towind, but was less common on steep slopes with thin soils, where akiraho, kohuhuand titoki were co-dominant. Ngaio mainly occurred on those steep slopes withthin soils that had a northerly aspect. Karaka and rangiora showed strongpreferences for sheltered sites or those with southerly aspects, though karaka andmahoe can thrive on quite mobile screes. Loess soils (Paremata hill soil and Poriruafine sandy loam) had tawa and miro in the canopy and previously had totara. Fivefinger was only evident on these richer soils in sheltered sites. Titoki was foundmainly on well drained soils and was not common on slow draining loess loams,whereas kohekohe appeared tolerant of a wide range of drainage conditions. Onquick draining soils (Terawhiti steep-land soils and Titahi hill soils) manuka andkanuka dominated recolonisation, followed by mahoe, tree ferns and kaikomako. Inshady, sheltered sites rangiora, five finger, kawakawa and hangehange followed, withthe latter two species persisting under a closed canopy at all sites. In exposed siteson well drained soils small-leaved Coprosma species and New Zealand broomestablished first. On less well drained soils regeneration was dominated bybroadleaved species, with pigeonwood present.

Timmins et al. (1987b) listed 36 species of trees and shrubs suitable for propagationand planting on Mana Island; of these, 22 have been recorded naturally from ManaIsland, and 12 were recorded at sites surveyed by Ogle (1985) and Gabites (1994).The two remaining species (akeake and Pseudopanax anomalus) are rare or absentfrom forest remnants on the coastline near Mana Island. There may be no naturalakeake present on the Wellington coast of Cook Strait Ecological District, but P.anomalus is common in shrublands on Kapiti Island.

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Figure 5.3 Distribution of sail types of Mana Island (after Heine 1975).

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TABLE 5.3 VEGETATION COMMUNITIES TYPICAL OF THE SOIL TYPES PRESENT ONMANA ISLAND AS DETERMINED BY SURVEYS OF FOREST REMNANTS ON THEADJACENT COAST (OGLE 1985; GABITES 1994).

2 2

*(nearest mainland equivalent to Paremata silt loam)

SOIL TYPE PAREMATA PORIRUA FINE TERAWHITI TITAHIHILL SOIL' SANDY LOAM STEEP-LAND SOILS HILL SOILS

Soil Loess and weathered Loess on rolling Greywacke and Deep, soft consolidateddescription greywacke on grey- country, slow greywacke scree on sand. Prone to erosion.

wacke. Moderately drainage steep slopes. Rapid Excessive drainagewell drained drainage

Sites Karehana Bay Steps Rangi's Bush; Raroa Reserve (true right); Raroa Reserve (true left);surveyed (deep gully);Track Pikarere Homestead West Wairaka Point; Brews Bush;Airlie Road

Bush, Plimmerton (upper slopes) Paekakariki Hill Rd; Clarke(spur crest) Reserve; Pikarere

Homestead; North PikarereHomestead (lower slopes);SH1 escarpment

Dominant Kohekohe, tawa Kohekohe, tawa Kohekohe, karaka Kohekohe, ngaiocanopy species

Other Karaka, titoki, miro, Mahoe, hinau, Akiraho, kohuhu, titoki, Tawa, kahikatea,canopy wharangi, heketara, wharangi, kohuhu, wharangi, kaikomako, kaikomako, totara, miro,species ngaio, totara, large-leaved kaikomako ngaio (northerly rata vines

milk tree, matai, cabbage aspects)tree

Dominant Mahoe, kawakawa, Kawakawa Kawakawa Kawakawa,understorey hangehange hangehange

Other Rangiora, Rangiora, mapou, Rangiora, mahoe, Mahoe, Coprosmaunderstorey Coprosma areolata, hangehange, pigeon- hangehange, rhamnoides, lancewoodspecies pigeonwood, ramarama, wood, raurekau, pigeonwood, five finger,

rohutu, kiekie Coprosma rotundifolia mapou, karamu

Seral Manuka, mahoe and Mahoe, pigeonwood Tauhinu, kanuka, Manuka, kanuka, mahoe,species other broadleaved Coprosma areolata, tree ferns, rangiora, five

species with early C. propinqua, fingerappearance of C. rhamnoides,canopy species, C. rotundifolia,coastal tree daisy NZ broom, koromiko

Lianes Metrosideros diffusa, Aka, Metrosideros Aka, aka kiore, Metrosideros fulgens,M. fulgens, fulgens, kaiwhiria, kaiwhiria, kohia, aka, Muehlenbeckiaaka, kiekie, kaiwhiria, supplejack pohuehue, australis, kaiwhiria,supplejack, kohia, Muehlenbeckia kohia, supplejackpuawananga australis, supplejack

Other tree Wineberry, karamu, Coprosma Wineberry, puka, Titoki, hinau, putaputaweta,and shrub Coprosma rotundifolia, rhamnoides, lancewood, pate, Coprosma areolata,species puka, rewarewa, kanuka, C. areolata, kapuka milk tree C. rotundifolia,recorded from northern rata, mapou, C. propinqua, C. lucida,this soil type kaikomako, kohuhu, raurekau, karamu, mingimingi,

five finger, lancewood, mapou, koromiko, ramarama,nikau, pukatea, white northern rata, kohuhu,maire, kahikatea, rimu nikau, swamp maire

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TABLE 5.4 NATIVE TREES, SHRUBS AND LIANES NOT NATURALLY OCCURRING ONMANA ISLAND BUT PRESENT ON SIMILAR SOIL TYPES AND SITES ON THE ADJACENTMAINLAND. THOSE SPECIES ASTERISKED HAVE ALREADY BEEN USED DURING THEMANA ISLAND PLANTING PROGRAMME.

5.6

A REVEGETATION STRATEGY FOR MANA ISLAND

The following revegetation strategy is based on:

(a)

Gabites' (1994) and Ogle's (1985) surveys (see Table 5.3)

(b)

the distribution of different soil types on Mana Island (Figure 5.3)

(c)

the areas identified for revegetation (Figure 5.1)

(d)

past experience with survival of plantings in different sites

(e)

specific habitat requirements of species such as kahikatea, pukatea andswamp maire

Predominant species for planting on each soil type are asterisked.

Paremata silt loam (plateau north of both KaikomakoValley and House Valley)

Loess, moderate drainage.

Initial plantings

mahoe*, karamu*, pigeonwood, ngaio*(thin out later), tree Lucerne*(remove later),karaka (south facing gullies), kohuhu, coastal tree daisy, five forger, cabbage tree.

Subsequent interplanting

kohekohe*, tawa*, wharangi, titoki, miro, totara, large-leaved milk tree, rewarewa,white maire, matai, rimu, kawakawa*, hangehange*, rangiora, kiekie (in gullies),ramarama, rohutu.

2 3

DICOT TREES AND SHRUBS

wineberry raurekau rimu kapukapukatea white maire totara* lancewood*tawa* Coprosma ro tundifolia hinau pigeonwood*ramarama heketara miro* pateputaputaweta* kahikatea* hangehange* rewarewa*rohutu kohuhu* matai swamp maire

DICOT LIANES

puawananga kohia R. schmideltoides Metrosideros diffusaRubus australis M. fulgens R. cissoides

MONOCOT LIANES AND TREES

nikau*~

supplejack

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Porirua fine sandy loam(south east plateau, south of Weta Valley)

Loess, poor drainage.

Initial plantings

mahoe*, ngaio*(thin out later), pigeonwood, kohuhu, Coprosma spp., mapou.

Subsequent interplanting

kohekohe*, tawa*, hinau, wharangi, kaikomako, kawakawa*, hangehange, rangiora.

Terawhiti steep-land soils (north side of Weta Valley,Kaikomako Valley, House Valley)

Assuming an initial planting density of 6000 plants/ha, a further 260,000 plants willbe required before initial planting of 72 ha is complete. A further 70,000 trees ofcanopy species (1000/ha) and 70,000 plants of subcanopy species (also 1000/ha)will be required during interplanting, which is in its initial stages on Mana Island.This suggests that a total of about 400,000 trees and shrubs will be required from1997 onwards to complete the planned restoration of forest communities on ManaIsland (Table 5.5). If annual plantings of 35,000 trees and shrubs can be achieved,the planting programme will take a further 11 years to complete, i.e., through to theyear 2007A.D.

When the forest structure is established, work can begin on restoring groundcoversand Hanes to each forest type (see species lists in Ogle 1985;Timmins et al. 1987a;Gabites 1994). As most lianes, ferns, herbs, sedges and grasses mature quickly, largescale planting should not be necessary. Once a seed source is established withinappropriate habitats, natural processes should ensure the rapid spread of eachspecies if conditions are suitable.

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Steep slopes with rapid drainage.

Initial plantings

Coprosma spp.*, mahoe*, mnuka*, koromiko*, ngaio*(north facing slopes), akiraho,kohuhu, mapou, five finger.

Subsequent interplanting

kohekohe*, karaka* (south facing slopes), wharangi, titoki, kaikomako, large-leavedmilk tree, kawakawa*, rangiora, hangehange, pigeonwood, wineberry, puka, pate.

Titahi hill soils (low-lying areas west of houses, lowersections of Weta Valley and slopes to south)

Sandy soils, well drained.

Initial plantings

ngaio*, mahoe*, mnuka*, five finger*, Coprosma spp.*, manuka, kaikomako, kohuhu.

Subsequent interplanting

kohekohe*, tawa, kahikatea, totara, miro, titoki, hinau, northern, rata, swamp maire,pukatea, kawakawa*, hangehange*, rangiora, lancewood, putaputaweta, mapou, nikau.

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TABLE 5.5 ESTIMATED PLANT REQUIREMENTS FOR RESTORATION OF FORESTCOMMUNITIES ON MANA ISLAND 1997-2007.

This revegetation programme will produce forest types that will provide suitablehabitat for all the forest bird species proposed for translocation to Mana Island.Kohekohe-tawa-karaka forests are found over large areas of Kapiti Island, whichsupports abundant populations of little spotted kiwi, New Zealand pigeon, kaka,whitehead, robin, tui and bellbird - seven of the nine forest and shrubland birdspecies proposed for release on Mana Island. Yellow-crowned parakeets on theChetwode Islands are abundant in kohekohe forest, flax shrublands and regeneratinggrasslands, all habitats that are or will be present on Mana Island. Habitatrequirements of rock wren in the absence of mammalian predators are not known,but are likely to include open shrublands and rock falls such as occur on the cliffsand shore platform of Mana Island.

Most planting effort to date on Mana Island has focused on initial plantings, and sothere is little experience as yet of the success of interplantings of canopy andsubcanopy species. An iterative approach is therefore required to check whetherthe recommended species mix presented here will thrive at each planting site, andto modify the planting strategy accordingly.

2 5

I NITIAL PLANTINGS (263,000)

ngaio 59,000 koromiko 14,100 karaka 4,000karamu 48,000 pigeonwood 10,000 akiraho 3,500mahoe 37,500 tree lucerne 10,000 kohuhu 3,000Coprosma luctda 19,000 kaikomako 5,000 manuka 3,000kanuka 18,400 mapou 5,000 coastal tree daisy 1,000fivefinger 17,500 cabbage tree 4,800

INTERPLANTINGS OF CANOPY SPECIES (67,000)

kohekohe 28,200 wharangi 4,500 pukatea 400tawa 9,800 miro 800 swamp maire 300karaka 5,000 totara 800 kahikatea 300large-leavedmilk tree 5,000 northern rata 500 matai 300titoki 5,000 hinau 500 white maire 300kaikomako 5,000 rewarewa 4oo rimu 300

I NTERPLANTINGS OF SUBCANOPY SPECIES (69,500)

kawakawa 25,000 puka 3,700 putaputaweta 2,000rangiora 10,000 pigeonwood 4,900 mapou 2,000hangehange 9,900 pate 4,000 nikau 800wineberry 5,000 lancewood 2,000 kiekie 200